Transilluminated dial



Aug. 19, 1958 T. A. SMITH TRANSILLUMINATED DIAL 2 Sheets-Sheet 1 Filed Feb. 16, 1955 LWf l a INVENTOR THOMAS A. SMITH ATTORNEYS Aug. 19, 1958 T. A. SMITH ,9

} TRANSILLUMINATED DIAL Filed Feb. 16, 1955 2 Sheets-Sheet 2 THOMAS A. SMITH 2,847,970 Patented Aug. 19, 1958 TRANSILLUMINATED DIAL Thomas A. Smith, WilmingtomDcL, assignor, by mesne assignments, tothe United States of America as represented by the Secretary of the Navy Application February 16, 1955, Serial No. 488,731 6 Claims. (Cl. 116-129) The present invention relates, ingeneral to internally self-illuminated indicating dials, and morespecifically to an improved dial that is illuminated by internally conducting and orienting the rays of light of a centrally located light source to generate a uniformly illuminated dial wherein the dial indicia are distinct and internally illuminated to a high level of intensity.

In the operation of moving vehicles, itis important that the operator be apprised of discrete information by means of specific instruments. in an aircraft, for example, for safe flying procedures it is important that the pilot be continuously aware of the basic mechanical and aero dynamic conditions of the aircraft by means of instruments that must be read under varying light conditions from theextremes of direct sunlight to darkness.

Thus the level of light intensity of the 'dial must be variable in accordance with the surrounding'levels of light intensity, and said dial must also be uniformly illuminated to prevent fatigue-causing bright and dark areas.

This-invention satisfies the above requirements by utiliz ing a'single lamp or bulb that is located within close proximity to a centrally located aperture of a light conducting dial that contains specific indicia. The light from said lamp or bulb is captured and directed, radially, along the interior of said dial to emerge at varying distances from the place of entrance to generate an evenly illuminated dial.

At the present time, instrument dials are illuminated by light that is distributed in a parallel-wise manner'and the indicia illuminated by contrast. Saidpresent method results in the waste of many light rays and a dial that has an irregular and very low level of intensity.

This invention consists of a light conducting dial that has engraved or coated indicia on the face of said dial. The top of the dial is fiat. The bottom of the dial is tapered, it beingthinner at the edge than at the center. The light rays enter the dial at the center, travel parallel to the top surface of the dial until contact with the lower tapered surface is made, and are then redirected towards andthrough the top surface to illuminate the indicia. This device thus directs a major portion of the light rays that enter the dial to spray the indicia areas. The indicia areas are sprayed by a multitude of.divergent light rays, thus resulting in .indicia that are sharp, and at a high level of illumination.

One object of this invention is to provide an instrument dial that contains discrete information and thatconducts light toenable an observer to easily read saiddiscreteinformation;

Another object is to luminated;

An additional objectis to provide an instrument dial that is preshaped so that discrete information on said dial is uniformly illuminated and clearly readable; and

Another object is to provide an instrument dial that well defined,

provide a dial thatis centrally il- 'is highly illuminated by the utilization of light from a single'centrally located lamp.

,trical contact with said cap Other objects and many of the attendant advantages of this invention will be' readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein;

Fig. l is a front view of an indicating instrument such as an oil pressure, speed or temperature instrument that is mounted on an instrument panel, showing a preferred embodiment of the invention;

Fig. 2 is a vertical cross section, with portions broken away and parts shown in elevation, of the instrument illustrated in Fig. 1;

Fig. 3 is a cross section view of the dial; and

Fig. 4 is a cross sectional view of the plug assembly for the feeding of current to the lamp assembly.

Similar numerals refer to similar parts throughout the several views.

The indicating instrument comprises a body or casing 2 that is adapted for mounting on an instrument panel 4 by means of screws or bolts 5. The dial 78 contains discrete information in the form of lines and numbers that are indicated by the position of the pointer 84. (In Fig. l, the pointer is shown at rest on the zero position.) Located directly over the pivot axis of the pointer 84 is a lamp and housing 24 that provides illumination for the dial 78.

All instruments that are utilized within an airplane must have anti-fogging means, and many such instruments require an hermetically-sealed casing for accurate operation. The hermetical sealing of an instrument may be accomplished in the manner indicated in Fig. 2. The body creasing 2 is cup-shaped and contains an airtight electrical coupling 6 at some convenient location 14. The sealing is completed by means of a transparent glass or plastic front 8 that sits on a ring gasket 10 that may be made ofrubber. Said gasket 10 is in contact with the lip or ledge 12 of the body 2. A second ring gasket 16, that may 'also be composed of rubber, is located immediately above said gasket 10 and in close contact with the upper surface of the glass 8. A ring 18 is secured to the body 2 by bolts 20. Said bolts 20 draw the ring 18 down, thus compressing the gasketlli tightly between the glass face i; and the ledge 12 to form an air-tight joint.

The face plate 8 is coated with a transparent electrical conducting coating on each surface '7 and 9. This coating enables current to flow across the surface of the face plate 8. The coating is only on the surfaces 7 and 9 and not on the edges 11 and 13 of said face plate 8. Thus there is no direct electrical path between said surfaces 7 and 9, as said face plate 8 is composed of a transparent insulator such as glass or plastic. A hole 22 in the center of the face 8 accommodates a lamp and housing 24. A cylindrical electrical contact 26 having a flanged end 28 is mechanically connected as by solder to the face 8, and electrically connected to the conducting coating that is on the surface 9'. This connection results in an airtight joint. A second cylindrical contact 30 is mechanically connected to said face 8 and electrically connected to the conducting coating on the surface '7 in a mannerthat is similar tothe coupling between said contact 26 and said face 9. The contact 34 is provided with internal screw threads. Thus, there is no direct electrical connection between the two contacts 3%) and 26. A hollow electrical conducting cap 32 has external screw threads 34 that engage with the internal threads of the contact 30. An insulating sleeve 36, of hard rubber or Bakelite, is cemented to the interior wall 38 of the cap 32. Said sleeve 36 contains an (inwardly positioned lateral projection 40. A conventional lamp 42 is positioned between said projections 40 and is retained in place by well known means to make one elec- 32 at the point 44. An electrical conducting bulb-contact cylinder 46 is cemented to the interior wall of the insulating sleeve 36 and butts against the abrupt projection 40 of said sleeve 36. Said sleeve 46 makes the second electrical contact with the bulb 42. A rubber gasket 48 is provided at the lip of the cap 32 to seat on the end of the cylindrical contact 26 to complete the hermetical sealing of the unit.

Current is brought to the lamp 42 by means of brushes that are located within the ring 18 and contact the conductive coatings on each surface 7 and 9 of said face 8. i

The brushes receive current from female connector plugs located within the body 2 of the unit. Securely attached to the ring 18, is the male plug assembly 50. Said assembly comprises an electrical conducting brush or strip of spring-tempered metal 52 to function as a brush contact. It was found that when said brush 52 was made of beryllium copper it functioned in an acceptable manner. One end of said brush 52 is sandwiched between two insulating plates 54 and 56 which may be fabricated from a material such as hard rubber, for example. Said plate 54 contains provisions for mounting to ring 18 by means of screws or bolts. An electrical conducting prong 58 of brass or beryllium copper is rigidly connected to the insulating plate 56 and is electrically connected to the brush 52. The prong 58 and brush 52 are electrically insulated from the ring 18. Said prong functions as a male connector and is slidably connected to a female plug 66 located in a cutout portion of the body 2 and retained in position by any standard means such as cementing. The female plug assembly 60 comprises a plastic sleeve 62 that is accommodated by a circular channel in the body 2. A plastic cylindrical insert 64 is securely cemented to the plastic sleeve 62 and contains a centrally located longitudinally running hole 66 to accommodate the male prong 58. An electrical conducting contact bar 68 is cemented to the interior wall of the circular hole 66. An electrical conducting wire 70 is connected to the contact bar 68 at one end and to an input connector 72 at the other end. Said connector 7 2 is electrically insulated from and securely attached to the body 2. The brush 52 is positioned in a manner that will not disturb the hermetical sealing around the face 8. The brush 52 makes electrical contact by pressure, with the conductive coating on the surface 7 of the face 8. In a similar manner, an electrical connection is made with the conductive coating on the surface 9 of the face 8. An input connector 74- is electrically coupled to the second mentioned brush assembly. In practice the ring 18, lamp assembly 24, and face 8 may be removed by lifting up ring 18, after removing the bolts 20. It is thus noted that there is no rigid electrical connection between the body 2, the ring lid, the face 8 and lamp assembly 24. Therefore, it is possible to rapidly remove or replace the face 8 and the lamp 42 to replace faulty parts or to adjust the instrument movement within the body 2.

In operation of the lamp, a voltage is applied across the terminals 72 and 74. For convenience it shall be assumed that the flow of current is from the terminal 72 to the terminal '74. The flow of current is from the terminal 72, through the wire '76, to the contact bar 68. The prong 58 picks up the current and feeds it to the conductive coating on the surface 7, through the brush 52. The cylindrical contact 30 picks up said current and feeds it to the lamp 42 through the cap 32. The return path for the current is from the lamp 42, to the sleeve 46 to the cylindrical contact 26, to the conductive coating on the lower surface 9, to the second male plug assembly, to the second female plug and through to the terminal 7 4.

The electrical conductive coating on the two surfaces of the face 8 has a measurable interval resistance. As a result of this resistance, heat will be generated, and the face 8 will become warmed by the current that flows to the lamp 42, thus providing the heated face essential to "prevent fogging. A portion of this current is utilized to the terminal 74- through i light the bulb 42. Thus the instrument face contains antifogging means and illumination means and is coupled to the instrument body through a non-rigid, non-restrictive quick-disconnect electrical coupling.

Centrally positioned immediately below said lamp 42 is a dial 78 that is composed of clear plastic or glass.v Said dial is positioned relative to a standard meter movement (not shown) by standard means such as screws and studs. The center of said that accommodates the instrument dial hand shaft 82. The movement of said shaft 82 is controlled by the instrument movement located within the body 2. A pointer or hand 84 is connected to said shaft 82 to indicate the angular movement of the shaft 82 relative to the dial 78. The dial has a flat top surface 86 on which there is engraved indicia that represent discrete information. The lower portion of said hole is cut out and polished to form a conical prism 88. The back side of the dial plate '78 tapers from a relatively thick section 90. The back side of said dial is divided into approximately three equal parts, the center one third 90, and the end one thirds 92. The end third 92 tapers from the thick center section to a thinner edge 94. Said edge 94 is on a greatly increased angle. In the operation of the dial plate 78, light from the bulb 42 enters the dial at the top polished surface 96, as illustrated by the single ray of light 98 in Fig. 3. The conical prism 88 redirects the ray of light into the dial 78. At some point 100 the ray of light contacts the highly polished tapered section 92 and is redirected upward towards the top surface 86. At the location 102, the ray of light contacts the upper surface 86 that contains the indicia. At this location a portion of the ray 98 passes through the dial to illuminate the indicia, and the remainder is redirected to the edge 94 where it is redirected through the upper surface 86 at the location 104 to generate additional illumination on the indicia.

Thus it can be seen that this dial redirects a major portion of the light that enters the dial 78 to the indicia markings that are located near the edge of the dial in an abundance of high level uniform illumination.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A transilluminated dial comprising: a flat member having an upper surface and a lower surface which is tapered from the central portion to the outer edge so that said fiat member is thickest at its central portion, said central portion being angled to reflect light internally through the member toward the outer edge, the angle of taper of the lower surface being such as to direct the outer edge area of the flat member light reflected from the central angled surface and impinging upon said tapered surface; and lighting means mounted in front of said flat member and arranged to project light rays upon said central angled surface of said flat member.

2. A device as set forth in claim 1, wherein said outer edge is sharply angled whereby light transmitted through the interior of said flat member and impinging upon the angled surface of said outer edge is directed to the outeredge area of said upper surface.

3. An indicating instrument comprising: a support member; a dial of the circular type having a flat upper surface and a lower surface which is tapered so that the dial is thinnest at its peripheral edge, the lower surface of said dial being formed with a sharp angle in the central region such that light impinging upon said sharply angled surface from the direction of the upper surface is directed radially through the interior of said dial, the taper angle of the lower surface being such as to direct to the periphery of the dial light reflected upon said tapered surface from said sharply angled surface, said dial 78 contains a small hole 80 upper surface bearing indicia near its peripheral edge; lighting means mounted in front of said dial and arranged to project light rays through the upper surface upon the sharp angle of the lower surface; and an indicator arranged for movement with respect to said indicia.

4. A device as set forth in claim 3, wherein said lower surface is also sharply angled at the peripheral edge of said dial, whereby light transmitted through the interior of said dial and impinging upon said sharply angled peripheral surface is directed through the peripheral area of the upper surface.

5. An indicating instrument comprising: a support member; a dial of the circular type supported by said support member and having a flat upper surface and a tripartite lower surface, the part nearest the center being sharply angled so that light coming through the upner surface and striking the sharply angled surface is re flected internally in the radial direction, the middle part being tapered so that light coming from said sharply angled surface and striking the tapered surface is di rected to the peripheral edge of the dial, and the pe ripheral part of the lower surface also being sharply angled so as to direct impinging light upwards through the peripheral area of the upper surface, said upper surface bearing indicia upon its peripheral area; lighting means mounted in front of said dial and arranged to project light rays upon the sharply angled part of the lower surface nearest the center of said dial; and an indicator arranged for movement with respect to said indicia.

6. A transilluminated dial comprising: a dial of circular type having an upper and a lower surface, said dial formed with a central aperture shaped like a conical prism with its wider base toward said lower surface, said lower surface being tapered so that said dial is thicker in the middle than at the periphery, the side of said prism being angled so as to internally reflect in the radial direction incident light coming through said upper surface, the taper angle of the lower surface being suitable for reflecting to the peripheral area of the dial incident light reflected from the tapered side of said prism, said lower surface being sharply angled at the peripheral edge of the dial, whereby light transmitted through the interior of said dial and incident upon said sharply angled peripheral surface is directed through the peripheral area of the upper surface; and lighting means mounted in front of said dial and arranged to project light through said upper surface upon the tapered side of said prism.

References fitted in the file of this patent UNITED STATES PATENTS 

